Apri11983
Reduced Tillage Cropping
Systems for Southwest Kansas
Charles A. Norwood, Research Agronomist
Reduced tillage studies at the Garden City Experiment Station were initiated in 1971. Those studies
were designed to compare conventional (tillage. only)
systems with reduced tillage systems substituting herbicides for tillage. Weed control, retention of crop residue, moisture conservation, and yield are being
studied. The study reported here was begun in 1978
and is a comparison of the wheat fallow (WF) , sorghum fallow (SF), continuous sorghum (SS), and
wheat-sorghum-fallow (WSF) systems.
Procedure
The WF system consists of three treatment~. The
first is a tillage only treatment where no herbicides are
applied; only blades or rodweeders are used for weed
control. The second consists of lib of atrazine applied
after wheat harvest, followed by tillage as required
when the herbicide no longer controls weeds. The
third treatment consists of the application of 1 lb of
atrazine following wheat harvest, 2.4 lbs of Bladex in
April of the following year, and tillage when the herbicides degrade. The WSF system consists of three simi-
Table 1. Effect of herbicides on the number of tillage operations during fallow in the wheatfallow and wheat-sorghum-fallow systems.
Herbicides
1979
1980
Wheat-fallow
Tillage only
1.0 lb Atrazine
1. 0 lb Atrazine
+ 2.4lbs Bladex
(Sequential)
1981
1982
Avg.
No. of Operations
7
5
5
3
7
5
9
7
7.00
5.00
4
2
3
4
3.25
4
2'
3
1
3
1
4
2
3.50
1.50
0
0
0
0
0
Wheat-sorghum
-fallow
Tillage only
2.0 lbs Atrazine
2.0 lbs Atrazine
+ 1. 6 lbs Bladex
(Sequential)
lar treatments except that 2 lbs of atrazine are applied
in the second and third treatments, and 1.6lbs Bladex
is applied in the third treatment. There is no tillage for
weed control in the third treatment of the WSF system. Conventional tillage practices usually are followed for sorghum in the SF and SS systems, and
prior to wheat in the WSF system.
Results: Tlllage Reduction
Table 1 shows the number of tillage operations for
each treatment in the WF system, and prior to sorghum in the WSF system. In the WF system one or
two operations per year were saved by applying atrazine. The addition of Bladex in the spring saved an additional one to three operations. Therefore, application of atrazine followed by the sequential application
of Bladex reduced the average number of tillage operations by about one-half. In the WSF system, atrazlne followed by sequential Bladex eliminated all tillage and allowed no-till sorghum to be planted. Two
pounds of atrazine alone allowed the elimination of
two tillage operations in each year.
Results: Yield
Table 21ists sorghum yields in the WSF, SF, and SS
systems. In the WSF system, a significant increase in
yield due to a reduction in tillage occurred only in
1981, however, there was a trend toward increased
Table2. Yield of sorghum as affected by cropping system and herbicides.
Wheat~sorghum
Tillage
System
Sorghumfallow
Continuous
sorghum
Year
-fallow
1979
49a'
51 a
57 a
Tillage Only
Min Till
NoTlll
56 a
54 a
57 a
59
1980
Tillage Only
Min TUI
No Till
60a
56 a
70b
84
44
1981
Tillage Only
MinTIH
NoTlll
72a
73a
76a
79
71
1982
Tillage Only
MinTIH
No Till
59
71
Avg
58
..
Tillage Only
Min Till'
No TilP
)
-Bu/ A64
65
Yields within a column In the same year followed by a different letter are significantly different at the 10% level.
Yields In the WSF, SF, and SS Systems differ s!gnUicantly in 1981 at the 10% level.
' •' Min TU! is 2 lbs Atraz!ne after wheat hi!irvest. No TUiis 2 lbs Atrazlne after wheat harvest + 1.6 lbs Bladex the next
spring.
1
)
yields in 3 of the 4 years. The trend indicates that a
yield increase may be more likely with no tillage at all,
rather than a reduction in tillage. This may be because
of the effect of the stubble in reducing evaporation
from. the soil surface after the sorghum is planted.
Unlike the research in other areas, the results of .this
study indicate that essentially no additional soil moisture was stored in the soil profile during fallow in the
reduc~d and no-till treatments. This explains why
larger yield increases generally did not occur.
The yield in the SF system, while appearing to be
somewhat larger than WSF sorghum yields, was significantly larger only in 1981. This was due in part to
an additional 1. 7 inches of water being stored during
the fallow period. 1981 was the only year in which
more water was stored by planting time in the SF as
opposed to the WSF system. Usually the shorter fa!-
)
low periods in the WSF system have proven to be
more effective in storing moisture than the longer WF
and SF periods.
Continuous sorghum yields are somewhat inconclusive. The continuous sorghum plots were fallowed In
1979 to correct a sandbur problem so only 2 years'
data are available. The 1981 yield was affected by
average rainfall in April and May prior to planting fol-.
lowed by adequate growing season rainfall. The 1982
yield was affected by average winter and spring precipitation plus abnormally high growing season rainfall.
Wheat yields from the WF and WSF systems are
presented in Table 3. Wheat yields were unaffected by
treatment. Over one inch of moisture was saved by reduced upage prior to planting the 1981 crop, although
no increase in yield occurred . A late freeze during
heading may have reduced the yield of the 1981
Table 3. Yield of wheat as affected by cropping system and herbicides.
Herbicides
1980
1981
Avg.
1982
Tillage only
1.0 lb Atrazlne
1 .0 lb Atrazine
+ 2.4lbs Bladex
45a2
41 a
Bu/ A Wheat-fallow
32a
54 a
31 a
50 a
44a
32a
TUia!;!e only
2 .4lbs Bladex
40a
39a
1
44
41
54 a
43
Bu/ A Wheat-sorghum-fallow
20b
51 a
24b
51 a
37
38
1
Wheat-fallow yiekls correspond to 1979, 1980, and 1981 tillage operations in Table 1.
• Yields within a column followed by a different letter are slgnlflcantly different at the 5% level.
wheat, possibly eliminating any respon~e to moisture.
Above average rainfall in May could have reduced any
response also. WSF wheat yields were lower than WF
yields only in 1981. The reason is unknown , but it
may be related to the late freeze or perhaps a slight difference in stage of growth between the two systems.
Soil ·molsture at wheat planting did not differ between
the WF and WSF systems in any year.
Summary
The proper selection and use of herbicides has allowed a reduction of one-half of the tillage operations
in the WF system and the. elimination of all tillage prior
to sorghum In the WSF system. When cropping systems were compared, sorghum yields from the wsr
system were less than SFyields In only 1 of 4 years,
while wheat yields from the WSF system were less
than WF yields In 1 of 3 years. Even if WSF yields
were reduced more often, obtaining two crops in three
years with the WSF system would tend to compensate
for any increased yield of the SF and WF systems.
Contribution 83-50-S, Garden City Branch
Experiment Station
Agricultural Experiment Station, Manhattan 66506
l1i41QI
Keeping Up With Research 69
Aprll1983
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4-83-3M